James p



(No Model.)

' J.,P. FREEMAN.

MAGNBTO TELEPHONE.

Patented May 16,1893.-

awvewtoz v UNrrEn STATES"? PATENT OFFI JAMES P. FREEMAN, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO MARVIN O. STONE, OF SAME PLACE.

MAGN ETD-TELEPHON E.

SPECIFICATION forming part of Letters Patent No. 497,649, dated May 16, 1893.

Application filed May 16, 1892., Serial No. 433,186. (No model.)

To all whom it may concern:

Be it known that 1, JAMES P. FREEMAN, of Washington,in the District of Columbia, have invented a new and useful Improvement in- Magneto-Telephones, of which the following. is a specification.

This invention relates to magneto-electric l telephones, and its object is namely, to increase the sensitiveness of the instrument and adapt the same for use over longlines.

To this end the invention consists essentially in the combination of a permanent magnet, and an insulated'coil or helix arranged in, the magnetic field between the two poles of the magnet in such manner that the lines of force extend at right angles to the convolutions of the helix, or substantially so.

In the accompanying drawingsz-Figure 1 represents a longitudinal vertical section through my instrument on the line 11 of Figs. 2 and 3; Fig. 2 a View looking into the receiving end of the instrument; Fig. 3 a view of the instrument from the opposite end. Fig. 4 is a view similar to that of Fig. 1, showing the instrument in modified form.

Referring to Figs. 1 to 3, A represents a compound permanent magnet, consisting of four U-shaped magnets a, having their inner and shorter legs joined to a central plate B of rubber, gutta-percha, or other non-conducting material B, and also having their outer and longer legs firmly attached to an iron ring 0,

or any conducting material, they should becountersunk, as represented in Fig. 1, so as to be out of contact with the base of the core in order to secure the perfect insulation of the latter.

Upon the non-conducting plate B, fixed to the inner poles of the magnets, I secure a soft iron core F, extending upward and terminating near the under surface of the iron diaphragm. Around the core F, which is wholly insulated from the magnets and from the diaphragm I place a coil or helix G of insulated tically so.

mouth-piece from the external'atmosphere core lies in the strongest portion of the magnetic field, and that the lines of force traversing the fields from the inner poles of the ma net to the diaphragm, which constitutes the opposite pole of the magnet, extend at right angles to the convolutionsof the wire, or prac- Openings e are made through the into the internal chamber above the dia- 4 phragm.

When speech is uttered in front of the mouth-piece the air sets upavibration of the diaphragm D immediately in front of the core F, which is rendered magnetic by induction. As the vibration of the diaphragm to and from the core F affects its magnetic force, a current constantly varying to correspond with the vibrations'of the diaphragm is set up in the coil G, whence it traverses the line H to a corresponding instrument at the opposite ing medium. Owing to the fact that the insulated magnet and its helix are located directly between the poles of the permanent magnet, I find the instrument to be extremely sensitive in its action, that the current developed is of great volume, and that the instrument will work successfully and give a distinct enunciation over longer lines than magnetic instruments of ordinary construclJlOIl.

Referring to the modified form of instrument represented in Fig. 4, A represents a compound permanent magnet, F an insulated core on its inner poles, and G, the encircling coil or helix; all constructed as in the first example. 0 represents an iron ring or plate with a small centralopening fixed to the upper outer arms of the magnet and forming the upper pole of the magnet. the diaphragm of iron peripherally supported by the ring 0', but insulated therefrom by the intervening strips 0 of non-conductingma- D represents ICO terial such as paper or gutta-percha. It will be observed that in this form of instrument like the first the electro magnet and its coil are both arranged between the magnetic poles, in the strongest part of the magnetic field, and in such position that the lines of force lie at right angles to the plane of the coils, or practically so.

While I prefer to retain substantially the details of construction herein shown, it will be understood by the skilled electrician that the essential feature, the a1 rangement of the insulated coil and its core in the magnetic field so that the lines of force out the coils at right angles, may be embodied in many different forms, the equivalents of those herein shown.

Having thus described my invention, what I claim is- 1. In a magneto telephone, the combination of a permanent maguet,a metallic diaphragm connected with one pole thereof, an insulated core mounted upon the other pole with one end adjacent to the diaphragm, and a helix wound about the core, the parts being so disposed relatively to each other that the lines of force between the poles of the magnet cut the coils of the helix at right angles.

2. In a magneto telephone the combination of a compound permanent magnet composed c of a series of U-shaped members, a metallic diaphragm mounted upon the arms composing one pole, an insulated core mounted upon the arms composing the other pole with its projecting end adjacent to the diaphragm, and a helix wound upon the core, the coils lying in the magnetic field in planes at right angles to the lines of force.

3, In a magneto telephone a permanent magnet composed of a series of U-shaped members arranged with legs of similar polarity adjacent to and parallel with each other, and the legs of opposite polarity radiating therefrom as from a center, a metallic diaphragm mounted upon the outer poles, a core and helix mounted upon the inner poles and insulated therefrom,the helix being disposed in the magnetic field, and its coils lying in planes substantially at right angles to the lines of force. a

In testimony whereof I hereunto sell my hand, this 8th day of April, 1892, in the presence of two attesting witnesses.

JAMES P. FREEMAN.

lVitnesses:

W. R. KENNEDY, RAYMOND F. BARNES. 

